0 °C is better?- Thawing temperature optimization study for cancer cryoablation in a mouse model with green fluorescent protein-labeled Lewis lung cancer

Purpose There are two kinds of thawing temperatures commonly adopted in cancer cryosurgery. We attempted to compare their efficacy differences in this study to optimize the surgical method. Method Forty-five C57BL/6 J mice with GFP-labeled Lewis lung cancer were randomized into three groups ( n = 15 for each): control group, T0 group (thawing temperature 0 °C), and T40 group (thawing temperature 40 °C). Cryoablation was performed using a combined surgical system. When the ice ball reached the border of the tumor, they were rewarmed to 0 °C and 40 °C, respectively, using a single freeze–thaw cycle. After the surgery, weight of these mice, length/width and the fluorescence intensity (FI) of the tumors were recorded. All mice were sacrificed on Day 14 after the procedures and their xenografts were excised and weighed immediately. We also checked for pulmonary metastasis, and examined tumor specimens using HE staining. Results Body weights, tumor volumes and FI in the three groups did not differ significantly at baseline. On Day 14, 39% of the tumors in the T0 group decreased in volume, whereas only 17% in the T40 group did. The average FI in the control group increased by 60%, but declined by 72% in T0 mice and 69% in T40 mice. Tumor inhibition rates were 71.64% in the T0 group and 68.12% in the T40 group. Lung metastases rates and histological changes were compatible between the two intervention groups. Conclusion Using 0 °C as the thawing temperature may have more potential benefits in cryoablation efficacy.